Hi, Guy...
The washers are fine, but that is not your biggest source of the GL. You will need to unplug everything and work backward from the amps (upstream) toward your sources, plugging one source's signal in at a time, until you find the culprit. That signal will need to be isolated from the system using some isolation transformers. There is a thread here somewhere that discusses this. Radio Shack has a cheap and very effective cable for this - works great.